MOLECULAR STUDY OF THE GERMINAL REVERSIONS INDUCED AT THE WHITE-IVORYLOCUS IN DROSOPHILA-MELANOGASTER

The white-ivory somatic mutation test of Drosophila melanogaster is ba sed on the reversion of the X-linked eye colour recessive mutation whi te-ivory to wild-type, Although the exact mechanism of white-ivory rev ersion is not quite understood, it has been suggested that such revers ion, both in somatic and germ-line cells, could be due to the precise excision of the tandemly duplicated 2.96 kb DNA fragment characteristi c of the,white-ivory mutation, We have attempted to confirm this hypot hesis analysing, at the molecular level, different germinal revertants induced by chemical treatment with three well known alkylating agents : ethyl methanesulphonate, methyl methanesulphonate and N-nitroso-N-et hylurea. The molecular analysis of these germ-line revertants, using S outhern blot hybridization and polymerase chain reaction techniques, s hows that such reversions are associated with the deletion of the 2.96 kb tandemly duplicated DNA sequence of the white-ivory locus.